<div class="uk-panel uk-panel-box">
    <h3 class="uk-panel-title">Nav side in panel</h3>
    <ul class="uk-nav uk-nav-side uk-nav-parent-icon" data-uk-nav>
        <li class="uk-active"><a href="">Active</a></li>
        <li class="uk-parent">
            <a href="#">Menu1</a>
            <ul class="uk-nav-sub">
                <li><a href="">Sub item</a></li>
                <li><a href="">Sub item</a>
                    <ul>
                        <li><a href="">Sub item</a></li>
                        <li><a href="">Sub item</a></li>
                    </ul>
                </li>
            </ul>
        </li>
    </ul>
</div>